Personal injury law has many complexities and requires an understanding of not only tort and insurance law, but litigation and trial procedures and of how insurance companies operate that a general practitioner may not possess.
Additionally, well-experienced personal injury attorneys understand how particular factors will influence the value of a claim. Comparative negligence issues (who was at fault, and to what degree), punitive damage issues, and pre-existing medical conditions of the claimant will also factor into the value of a claim. A serious personal injury attorney will have access to resources that give them up-to-date information about the claim value of various types of injuries.
One size does not fit all in the practice of law. Just as you would not seek treatment from a family practice physician for a traumatic brain injury, you should be equally careful in hiring a lawyer who has extensive experience representing injured people and working with insurance companies.